Green algae of the genus Chlorella are widely distributed on the Earth, from the Frigid Zones to the Torrid Zone, and are single-cell organisms of nearly spherical form measuring 2-10 μm (micrometer) in diameter. The utility of chlorella has been mentioned variously in folklore and academic reports; representative effects thereof include animal and microbial growth promoting effects, taste corrective and deodorant effects, plant hormone effects and the like. Medically, chlorella is known to have cell activation action, growth promotion action, immune function improvement action, detoxication action, antiulcer action and the like.
Likewise, the chlorella extract obtained by being extracted from chlorella algal cells with aqueous solvent also exhibits bioactive actions. Since chlorella extract exhibits growth promotion action on bacteria, yeast, protozoans and the like, it is called chlorella growth factor (CGF). Since the strength of the growth promotion action of chlorella extract corresponds to the absorbance of chlorella extract at 260 nm, chlorella growth factor concentrations are usually expressed by absorbance OD260 value.
Because this chlorella extract has been prepared by extraction with aqueous solvent, it contains amino acids, peptides, water-soluble proteins, saccharides, water-soluble vitamins, and nucleic acid-related substances, but it does not contain chlorophyll, fibers, and water-insoluble proteins, which are present in chlorella cells.
There are a wide variety of health foods making use of these bioactivities of chlorella; in addition to chlorella processed foods in the form of tablets and the like prepared by drying and powdering chlorella cells as they are, chlorella extract-containing foods prepared from a chlorella extract solution as the raw material are available.
Chlorella extract-containing beverages are disclosed in Japanese Patent Unexamined Publication Nos. HEI6-153876 and HEI7-79751, and are usually blended with chlorella extract, as well as with a sweetening agent, sour agent, antiseptic and other raw materials for beverage production and the like.
Disclosed in Japanese Patent Unexamined Publication Nos. SHO49-14661, HEI6-141812, HEI10-295298, and HEI11-46738 are various foods incorporating a chlorella extract-containing food additive as a food quality improver.
As stated above, a chlorella extract exhibits a wide variety of bioactivities, including growth promotion action on bacteria, yeast, protozoans and the like, so it is very rapidly perishable. For this reason, beverages containing a chlorella extract or food additives containing a chlorella extract are also perishable and are difficult to store. Furthermore, in the case of chlorella extract-containing beverages, even thermal sterilizing treatment is performed, bacteria, fungi and the like come therein after the stopper is removed, so it has been difficult to prevent the proliferation thereof.
For this reason, conventionally, chlorella extract-containing beverages have been stored, while coping with the flavor and stability issues, by combining a large number of sweetening agents and organic acids to adjust the drink to a pH of about 3, and adding a benzoate, which is a preservative in common use in beverages such as soft drinks and fruit juices.
However, benzoates have been shown to potentially produce benzene, a toxic compound known as a carcinogen, although in trace amounts, when ascorbic acid is co-present. For this reason, it is desirable that another preservative or a shelf life extender having sterilizing and antiseptic effects be used.
Meanwhile, as described in Japanese Patent Unexamined Publication No. HEI4-341169, capsicum extracts obtained by extraction with aqueous solvent are known to contain antifungal substances, and to be effective as food protecting agents. However, there is no knowledge of their influence on the quality, storability or shelf life of chlorella extracts.